KUALA LUMPUR, Malaysia — World sea piracy fell to its lowest level in five years in 2012, thanks to a huge reduction in Somali piracy, an international maritime watchdog said Wednesday.

The International Maritime Bureau said 297 attacks were recorded worldwide last year, down sharply from 439 in 2011. A total of 28 vessels were hijacked, with 585 crew members taken hostage and six killed during 2012, according to data compiled by the London-based bureau’s piracy reporting center in Malaysia.

The bureau said only 75 attacks were reported off Somalia and in the Gulf of Aden, down from 237 cases in 2011. Somali pirates hijacked 14 ships, half the total in 2011.

The bureau praised international navies patrolling the African waters, saying their preemptive strikes and robust action against mother ships helped deter piracy. Security measures by ships, such as hiring armed guards, also helped ward off pirates, it said.

“The continued presence of the navies is vital to ensuring that Somali piracy remains low. This progress could be easily reversed if naval vessels were withdrawn from the area,” said the bureau’s director, Capt. Pottengal Mukundan.

The bureau said pirate mother ships and skiffs were reported in the Gulf of Oman, southern Red Sea and the Somali basin. As at end of last year, Somali pirates still held 104 hostages on eight ships and 23 more were detained on land.

The report said waters off east and west Africa remained dangerous. Piracy rose in the Gulf of Guinea with 58 incidents recorded last year, including 10 hijackings and 207 crew members taken hostage. It said pirates in this area were particularly violent, with guns reported in at least 37 of the attacks.

Nigeria accounted for 27 incidents last year, up from 10 in 2011. Togo saw an increase from five reports in 2011 to 15 in 2012, including four hijackings.

The Ivory Coast had just one incident in 2011 but five in 2012, including the first-ever hijacking of a tanker off its shores.

Four vessels were hijacked in Southeast Asia, including a Malaysian tanker that was recaptured in Vietnam in the last quarter of 2012.

Across the Indonesian archipelago, the bureau said there were 81 reports of petty theft, accounting for more than a quarter of global incidents in 2012.